Recently, a tablet personal computer (tablet PC) which has a touch panel liquid crystal display and does not have a physical keyboard has rapidly become widespread. The tablet PC is easily carried and operation is easy since an input work can be performed through the touch panel.
However, since the tablet PC does not have a physical keyboard, for example, trouble occurs in an input work for inputting a long sentence in some cases. For example, there has been proposed a computer having a configuration in which a tablet PC that is an upper housing is detachable from a lower housing having a keyboard in Japanese Patent Application Laid-Open No. 2005-158013. Since such a computer can be used in two ways, as a laptop PC and as a tablet PC, it is very convenient for a user to use the computer.